During the procedure, gas is used to inflate the bowel using a thin, flexible tube placed in your rectum. CT scans are then taken from a number of different angles.

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As with a colonoscopy, it is necessary to take a special diet for a few days and take a laxative before the test to ensure that the bowels are empty when the test is carried out.

This test can help identify potentially cancerous areas in people who are not suitable for a colonoscopy because of other medical reasons.

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A CT colonography is a less invasive test than a colonoscopy, but cannot replace a colonoscopy or flexible sigmoidoscopy as the latter allow biopsies and examination of any abnormal areas to help make or confirm a diagnosis.